Value refers to the lightness or darkness of a hue, while hue is the pure color itself. Primary colors are red, yellow and blue that can be mixed to make secondary colors of orange, green and purple. Warm colors like red, orange and yellow are called such because they resemble the colors of fire. Contrasting colors are those opposite each other on the color wheel and can be used to make compositions more visually interesting. In Monet's Notre Dame Cathedral, colors are analogous while in Matisse's The King's Sadness colors are contrasting.